Supplementary Motor Area Encodes Reward Expectancy in Eye-Movement Tasks

Neural activity signifying the expectation of reward has been found recently in many parts of the brain, including midbrain and cortical structures. These signals can facilitate goal-directed behavior or the learning of new skills based on reinforcements. Here we show that neurons in the supplementary motor area (SMA), an area concerned with movements of the body and limbs, also carry a reward expectancy signal in the postsaccadic period of oculomotor tasks. While the monkeys performed blocks of memory-guided and object-based saccades, the neurons discharged a burst after a ∼200-ms delay following the target-acquiring saccade in the memory task but often fired concurrently with the target-acquiring saccade in the object task. The hypothesis that this postsaccadic bursting activity reflects the expectation of a reward was tested with a series of manipulations to the memory-guided saccade task. It was found that although the timing of the bursting activity corresponds to a visual feedback stimulus, the visual feedback is not required for the neurons to discharge a burst. Second, blocks of no-reward trials reveal an extinction of the bursting activity as the monkeys come to understand that they would not be rewarded for properly generated saccades. Finally, the delivery of unexpected rewards confirmed that in many of the neurons, the activity is not related to a motor plan to acquire the reward (e.g., licking). Thus we conclude that reward expectancy is represented by the activity of SMA neurons, even in the context of an oculomotor task. These results suggest that the reward expectancy signal is broadcast over a large extent of motor cortex, and may facilitate the learning of new, coordinated behavior between different body parts

Eye Movements and Reward, Sequential States, and Context-Dependent Target Selection

The eye movement system is a complete sensorimotor loop from sensation to action, which includes a large number of distinct cortical and subcortical regions and participates in both reflexive and voluntary behaviors. This dissertation elucidates some of the functions of three cortical areas known to participate in eye movement behavior: the supplementary eye fields (SEF), motor area (SMA), and the lateral intraparietal area (LIP). In the course of executing eye movements, the eye movement circuitry interfaces with other functional circuits, including the networks of brain structures involved in reward processing, the temporal organization of behavior, target selection, and object perception. Here it is shown how LIP, SEF, and SMA participate in these multiple functional circuits, and complement each other during eye movement tasks. First, it is shown that neurons in the SMA carry a reward expectancy signal in the post-saccadic period of oculomotor tasks. Second, the neurons of SEF, but not LIP, are shown to collectively encode the temporal progression of the task. Third, in a target selection task, most LIP neurons are shown to respond to both cue and distractor stimuli, while most SEF neurons respond selectively only to the cue. Finally, fourth, the spatial tuning of parietal neurons is investigated in more natural circumstances, and the directional tuning preferences of cells in parietal cortex are found to be task dependent. These results extend the understanding of how these cortical brain areas that participate in eye movement behavior specialize and complement each other, and how they interface with other brain circuits, to support the organism in successfully completing a variety of instructed tasks

A Neural Correlate of the Processing of Multi-Second Time Intervals in Primate Prefrontal Cortex

Several areas of the brain are known to participate in temporal processing. Neurons in the prefrontal cortex (PFC) are thought to contribute to perception of time intervals. However, it remains unclear whether the PFC itself can generate time intervals independently of external stimuli. Here we describe a group of PFC neurons in area 9 that became active when monkeys recognized a particular elapsed time within the range of 1–7 seconds. Another group of area 9 neurons became active only when subjects reproduced a specific interval without external cues. Both types of neurons were individually tuned to recognize or reproduce particular intervals. Moreover, the injection of muscimol, a GABA agonist, into this area bilaterally resulted in an increase in the error rate during time interval reproduction. These results suggest that area 9 may process multi-second intervals not only in perceptual recognition, but also in internal generation of time intervals

Proactive and reactive control by the medial frontal cortex

Adaptive behavior requires the ability to flexibly control actions. This can occur either proactively to anticipate task requirements, or reactively in response to sudden changes. Recent work in humans has identified a network of cortical and subcortical brain region that might have an important role in proactive and reactive control. However, due to technical limitations, such as the spatial and temporal resolution of the BOLD signal, human imaging experiments are not able to disambiguate the specific function(s) of these brain regions. These limitations can be overcome through single-unit recordings in non-human primates. In this article, we describe the behavioral and physiological evidence for dual mechanisms of control in response inhibition in the medial frontal cortex of monkeys performing the stop signal or countermanding task

The cognitive neuroscience of visual working memory

Visual working memory allows us to temporarily maintain and manipulate visual information in order to solve a task. The study of the brain mechanisms underlying this function began more than half a century ago, with Scoville and Milner’s (1957) seminal discoveries with amnesic patients. This timely collection of papers brings together diverse perspectives on the cognitive neuroscience of visual working memory from multiple fields that have traditionally been fairly disjointed: human neuroimaging, electrophysiological, behavioural and animal lesion studies, investigating both the developing and the adult brain

Very slow brain potentials relating to expectancy - The CNV

Very slow brain potentials and contingent negative variatio